Development of a Functional Health CAT for Managing Obesity Abstract In recent decades the prevalence of obesity has increased dramatically in the United States, causing a great burden for the individual and society. Although behavioral factors are among the most prominent causes of obesity and numerous weight management programs are currently offered, few practical instruments are available today to measure the functional health and other characteristics of obese adults that determine and define the success of weight management programs. We propose to use Item Response Theory (IRT) and Computerized Adaptive Testing (CAT) techniques to build a precise and short Patient-Reported Outcomes (PRO) instrument (OBESITY-CAT) to measure the impact of being obese on health-related quality of life (HRQOL) and self-efficacy expectations. CATs tailor the questions administered to each individual respondent, thereby increasing the precision and range of measurement without increasing respondent burden. In Phase I we propose to: (1) construct two item banks to measure the impact of obesity on HRQOL and the self-efficacy expectation to control weight, (2) develop a comprehensive and flexible OBESITY-CAT software solution, including immediate feedback reporting, and (3) pilot test the new tool in comparison with traditional full-length static questionnaires. To achieve these aims, we have partnered with Magellan Health Services, one of the nations' largest managed care organizations, serving 40 million individuals. Together we will develop obesity-specific items tailored particularly for the CAT process, analyze the item parameters in a sample of 1,000 of their employees (~ 75% being overweight or obese), and finally test the feasibility and acceptance of the OBESITY-CAT integrated into Magellan's nationwide weight management program in 100 participants. The product of Phase I will be a prototype comprehensive OBESITY-CAT with preliminary evidence regarding feasibility, acceptability, and empirical performance. In Phase II, the tool will be improved and further evaluated in terms of validity, reliability, and responsiveness, and its potential for use in predicting and monitoring treatment success, and the tool will be evaluated and programmed to be fully operational on different platforms, including PDAs and Interactive Voice Recognition (IVR). By greatly lowering data collection costs, reducing response burden, eliminating "ceiling" and "floor" effects and increasing the precision of individual scores, routine monitoring of HRQOL may become feasible as a clinical tool among obese adults. The Obesity-CAT will be able to monitor the success of weight management programs to increase the health related quality of life of overweight and obese adults. In addition, it will support tailoring weight management programs to the individual, and identify those which are at higher risk to drop-out of the program and need special attention. Compared to existing instruments, it will greatly lower data collection costs, reduce response burden, and increase the precision of individual scores, so that routine monitoring of HRQOL may become feasible as a clinical tool among obese adults. [unreadable] [unreadable] [unreadable] [unreadable]